This invention relates to an aerosol composition for the protection of polyolefins from light-induced degradation. When a polyolefin such as polypropylene is exposed to ultraviolet light for a period of time, particularly when exposed to sunlight, noticeable deterioration of the physical properties of the polymer is observed. On the theory that the polymer can be stabilized for a much longer period by preferential absorption of the radiation by another absorber, or by quenching of the absorbed radiation, various ultraviolet light stabilizers have been incorporated into the polypropylene composition. The disadvantages of this procedure include the imparting of color to the polyolefin by the ultraviolet stabilizer, limited compatibility of the ultraviolet stabilizer with the polyolefin and inefficient use of the stabilizer.
When a polyolefin is exposed to sunlight the greatest amount of deterioration occurs at the surface. For example, polypropylene moldings take on a dull cast due to surface crazing although the bulk of the molding retains its physical properties. Surface effects are also believed to predominate in the ultraviolet deterioration of polyolefin fibers, films, yarns, tapes, etc. Although it is the surface which requires protection from ultraviolet radiation, ultraviolet absorbers (stabilizers) are normally bulk-blended into the polyolefin. Only that portion of the stabilizer which is initially present near the surface or migrates to the surface from the bulk is believed to be effective in inhibiting the initiation of degradation. Consequently, a more effective use of an ultraviolet stabilizer would be to apply it directly to the surface where it is needed.
The surface protection of polymers by an ultraviolet stabilizer is described in U.S. Pat. No. 2,568,894. A composition of 2-hydroxy benzophenone and oxidized polymeric wax is disclosed in U.S. Pat. No. 3,429,841 for surface application to polypropylene. A problem in the prior art, leading to very limited use of surface application of stabilizers, is the difficulty of making the stabilizer adhere to the polypropylene and resist abrasion without producing a waxy or tacky surface which readily picks up dirt and soils. The solution to this problem is determinative of the usefulness of surface-applied protectorants to polyolefin textiles and carpets. The protectorant also must be compatible with the polyolefin and with the other materials found in combination with the polyolefin.